1. Field of the Invention
This invention relates to an improved sealing system for a valve which is employed downhole in a subterranean well in a high-temperature, high-pressure environment.
2. History of the Prior Art
It is the common practice in subterranean wells to incorporate one or more safety valves; for example, a flapper or a ball valve, in the lower regions of the wall, generally above the production zone of the well. In such location, the sealing elements of the valve are exposed to both a high-pressure and a high-temperature environment. The high presssure produces severe erosion of metallic sealing surfaces when they are cracked open, or just prior to effecting a complete closing, due to the erosion effects of particulates, such as sand, carried at high velocity past the sealing surfaces. The high-temperature environment encountered in modern wells of substantial depth prohibits the use of an elastomeric material as the primary sealing element, and forces reliance on employment of mutually engaging metallic sealing surfaces.
A valve construction which can effect a primary seal by engagement of metallic surfaces, yet protect such metallic surfaces against erosion through the utilization of a nonresilient, nonelastometric secondary sealing element which effects or maintains a minimal contact between the valve seat and the valve head during the final closing or the initial opening movements of the valve head, would be highly desirable.